1. Field of the Invention
The invention relates in general to a digital broadcasting technology, and more particularly, to a system and method for identifying a synchronization segment included in a control signal carried by multiple subcarriers in a digital broadcasting system.
2. Description of the Related Art
With progress in communication technologies, digital television broadcasting has also matured. In addition to being transmitted via cable wires, digital television signals may also be transmitted as wireless signals through equipments such as base stations or satellites. Integrated services digital broadcasting terrestrial (ISDB-T) is currently a prevelent standard in the field of digital television broadcasting.
Each data frame in an ISDB-T signal includes 204 orthogonal frequency division multiplexing (OFDM) symbols, each of which includes content bits carried by multiple subcarriers. According to ISDB-T specifications, a transmission and multiplexing configuration control (TMCC) subcarrier is for transmitting information including modulation types, encoding rates, scrambling lengths and multiplexing schemes for the reference of a receiver. In other words, one or multiple subcarriers in each symbol are dedicated for carrying the TMCC signal, and each TMCC subcarrier in each data frame carries 204 bits of information. In the 204 bits of information, the 2nd bit to the 17th bit (with a total of 16 bits) are defined as a synchronization segment.
Before decoding a received data stream, an ISDB-T receiver needs to first identify the synchronization segment in the TMCC signal in order to locate boundaries between data frames and to further determine positions and contents of TMCC information. The contents of the synchronization segment can only be one of two standard sequences—0011010111101110 and 1100101000010001. In the prior art, an ISDB-T receiver monitors whether a specific TMCC subcarrier in an input stream contains contents that match either of the above sequences. To enhance accuracy, after finding a matching 16-bit sequence, the ISDB-T receiver further determines whether another matching sequence is present at an interval of 204 bits. Only after having identified multiple successive matching sequences, the ISDB-T receiver performs a decoding procedure on the TMCC information. However, a setback of the above approach is that the ISDB-T receiver requires a long monitoring period before being able to locate the positions of the boundaries, such that a user of the ISDB-T receiver can only view contents provided by the transmitter after a long waiting period subsequent to boot-on.